Marcello gave me the tools necessary to be able to play essentially whatever I want and play well. With concepts like deciding the length of a pause, how to gradually change the tempo, and deciding how to contrast dynamics, I gained the tools necessary to make these decisions on future pieces and learn how to make a piece my own.
One of the most fun collections to play is Marcello's 5 seasons - one piece for each of the 4 seasons plus a finale. I even won first place in a competition with his finale piece, and I remember how happy he was that his own composition was competitive against a myriad of challenging classical pieces that only skyrocket in difficulty as the competition becomes tougher. I did a small amount of composing myself, and he helped with edits and performance advice.
During my final year in high school, I switched our lessons to focus on the trumpet, which I have done in band for a while but felt that I wanted more of a challenge. Marcello recognized that my attacks are soft, so we worked on opera style music to help me work on my weakness. I have not worked on solo pieces for trumpet, and Marcello introduced me to challenging and fun pieces: Sounds of the Hudson, Bride of the Waves, and the famous "Carnival of Venice". The Carnival of Venice is a wonderful piece, so I performed it at Marcello's concert. I even found accompaniment from an orchestra that I liked, so I wrote out chords for the piano and gave him the challenge of a custom piano support.
Before I left college, he introduced me to music chord theory. It was a great treat that I continued learning about in jazz electives at Michigan State. We also have hobbies in common. We played chess against each other and at first he was stronger but then I improved and managed to win and make games more competitive. During the years after lessons, we played tennis together and also had competitive games and another way to stay connected.
Perhaps the strongest outcome of our relationship was that I inspired my younger cousin Frankie to take lessons. Marcello said Frankie is the strongest piano player he has taught, with his ability to learn quickly and perform pieces that none of his other students have done, such as the 3rd movement of Beethoven's Moonlight Sonata if I remember correctly. He is likely one of the strongest competitors in competition as well.
I hope I gave insight into Marcello's versatility and advanced level of teaching.